The present application claims priority to Japanese Patent Application No. 2001-377801 filed in the Japanese Patent Office on Dec. 11, 2001 and Japanese Patent Application No. 2002-349,663 filed in the Japanese Patent Office on Dec. 2, 2002, the disclosures of which are hereby incorporated by reference herein in their entirety.
1. Field of the Invention
The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a facsimile machine, a printer, or other similar image forming apparatus, and more particularly relates to an image forming apparatus that forms images on transfer materials while repeating an electrophotographic image forming process including charging, image writing, developing, transferring, cleaning, and discharging steps.
2. Discussion of the Background
As an image carrier for use in an electrophotographic image forming apparatus, such as a copying machine, a facsimile machine, a printer, or other similar image forming apparatus, an organic photoreceptor made of organic photosensitive materials has been used because of its low cost, the ease of mass producing it, and because it is non-polluting. However, as compared to an inorganic photoreceptor, an organic photoreceptor has disadvantages, such as decreased durability and reduced abrasion resistance. Recently, a need has arisen for a photoreceptor having a small diameter because there is a demand for downsizing electrophotographic systems. A demand has also arisen for a photoreceptor having good durability against abrasion that increases in proportion to the number of copies. Thus, mechanical durability, which typically means abrasion resistance, is in strong demand.
Japanese Laid-open Patent Publication No. 1-170951 describes a method for improving the abrasion resistance of an organic photoreceptor whose surface includes a protective layer including a filler formed from a metal or a metal oxide. By this background method, a photoreceptor having a high mechanical durability can be obtained. However, in such an organic photoreceptor, the properties of the surface of the photoreceptor may be changed with time, because the surface of the photoreceptor is repeatedly charged with a charging device. As a result, toner from a toner image formed on the photoreceptor tends to adhere to the surface of the photoreceptor, and the transfer efficiency of the toner image formed on the photoreceptor can decrease, thereby causing an inferior image, such as a partial omission of a transferred image.
In order to prevent toner from adhering to the surface of the photoreceptor due to the surface property changes of the photoreceptor, a method has been employed in which surface energy of a photoreceptor is decreased by applying a lubricant onto the photoreceptor. As a background method of applying a lubricant onto a photoreceptor, Japanese Laid-open Patent Publication No. 2000-162881 describes a method of applying a lubricant onto a photoreceptor with a lubricant applying member, such as a brush. Further, Japanese Patent No. 2859646 and Japanese Laid-open Patent Publication No. 2002-229241 describe a method of applying a lubricant added to a toner onto a photoreceptor. By applying a lubricant onto a surface of a photoreceptor, the surface energy of the photoreceptor is decreased, thereby improving the mechanical durability of the photoreceptor and the transfer efficiency of a toner image, and preventing an occurrence of an inferior image, such as a partial omission of a transferred image.
With regard to the application of a lubricant onto a photoreceptor, some problems arise. When applying a lubricant onto a photoreceptor with a lubricant applying member, such as a brush, regular maintenance in terms of replacement of the lubricant is required. If a large quantity of lubricant is used to lengthen the maintenance interval, the size and cost of the apparatus increase.
On the other hand, when a lubricant is added to toner and applied onto a photoreceptor, fresh lubricant is applied to the photoreceptor by replacing a toner bottle. Therefore, as compared to the above-described case in which a lubricant is applied onto a photoreceptor with a lubricant applying member, maintenance of the lubricant itself and provision of the lubricant applying member are not required. However, there is a problem that the amount of the lubricant applied onto a photoreceptor depends on the area of the toner image formed on the photoreceptor. Specifically, when a large number of toner images are formed on the photoreceptor and toner for the toner images is transferred onto a transfer material, such as a transfer sheet, from the photoreceptor, a sufficient amount of lubricant added to the toner remains and is supplied onto the photoreceptor. However, when only a small number of toner images are formed on the photoreceptor, the amount of lubricant supplied onto the photoreceptor decreases accordingly.
According to an aspect of the present invention, an image forming apparatus includes an image carrier configured to rotate and carry an image on a surface of the image carrier, a latent image forming device configured to form an electrostatic latent image on the image carrier, a developing device configured to develop the electrostatic latent image with a developer including a lubricant, and a transfer device configured to transfer the developed image to a transfer material. The image forming apparatus further includes a control device including a lubricant application executing device and at least controlling the lubricant application executing device to execute an application of the lubricant to the image carrier by actuating the developing device to apply the developer to the surface of the image carrier during one job of an image forming operation from a start of rotation of the image carrier to a stopping of the rotation of the image carrier.